Under the contract the awardee will operate the NCI's Radiolabelled Chemical Carcinogen Reference Standard Repository. This entails purity analysis and distribution of labelled compounds on hand at the repository to researchers requesting their compounds. Other responsibilities are to resynthesize or repurify decomposed compounds not meeting purity standards and replenishing depleted stocks. Methods and synthesis pathways leading to the preparation of compounds not currently in the inventory are also to be explored. Synthesis of very unstable PAH metabolites such as the diolepoxides of various compounds and shipping them to the requestor is also a major requirement. This is due to synthetic expertise among repository staff. Money received in payment for compounds sold by the repository are used to defray NCI's cost in running the repository.